There are varying procedures and/or methods already known that lead to eliminate silicon contained in alumina based materials, such as:                a) U.S. Pat. No. 4,239,735 removes impurities from aluminas by solubilizing its contaminants and leaving the alumina in an insoluble phase. This is achieved by mixing kaolinite with at least 36 wt % of hydrochloride acid for dissolving impurities and converting the aluminum to insoluble aluminum chloride;        b) U.S. Pat. No. 4,304,575 describes a process that silica particles can be dissolved by heating with an alkaline solution thus settling them and creating bigger particles creating a silica sol where most of the particles have a much bigger size as they have before the process;        c) U.S. Pat. No. 4,560,541 refers to a method for eliminating soluble and non-soluble impurities, mainly sodium hydroxide and silica, by a reaction with stoichiometric amounts of hydrochloric acid in order to produce a reaction product such as chloride aluminum and aluminum chloride hexahydrate. After water addition, the solution is separated in order to eliminate insoluble impurities such as silica;        d) U.S. Pat. No. 4,973,462 describes a process for producing high purity silica by the direct addition of an alkaline silicate aqueous solution (water glass) to a mineral acid solution such as hydrochloric acid, nitric acid and sulfuric acid, in order to dissolve the impurities in the mineral acid solution and produce a silica precipitate; and        e) U.S. Pat. No. 5,242,670 details a process for the digestion of an inorganic silica/alumina matrix in order to produce silicon tetrafluoride and aluminum fluoride, in which the tetrafluoride in the gas phase or in solution contains aluminum fluoride and some other non-converted oxides.        
It is important to note that the conventional procedures and/or methods already known for eliminating or removing silicon contained in alumina based materials such as those already referred here above, use inorganic acids or a mixture of inorganic acids in a digestion step, thus modifying the alumina and any other element herein contained, thus destroying and avoiding for reusing the alumina based material.
The process of this invention constitutes an improvement over prior technologies known to applicants, which process eliminates silicon and/or silicon compounds contained in alumina based materials without destruction of the alumina based material, thus allowing the alumina based material to be reused. The main application of the process of the present invention is the regeneration of silicon-contaminated alumina based catalysts which are used in hydrotreating processes of the oil industry for sulfur elimination and silicon removal from hydrocarbon streams.
Therefore, the present invention provides a non-destructive process for the elimination of silicon and/or silicon compounds that are contained in alumina based materials, without destroying the alumina based material, thus enabling the alumina based material to be reused.
Another aspect of the present invention is to provide a non-destructive process for the breakdown and elimination of silicon and/or silicon compounds that are contained in alumina based materials, and is mainly employed for the regeneration of alumina based catalysts, used as silicon traps in hydrotreating processes of the oil industry, preferable in the hydrodesulfurization (HDS) processes of naphthas produced in a delayed coking process (coker naphthas).
Another aspect of the present invention, is to provide a non-destructive process for silicon breakdown and elimination of silicon and/or silicon compounds that are contained in alumina based materials, which process can break down the silicon compounds found as inorganic structures, as oxides or silanols: Si—(OX)4 (X═Al, H, Si) and/or as organic structures as organosilanes: (OX)3—Si—CH3 and/or (CH3)2—Si—(OX)2 (X═H, Si), without modifying the properties of the alumina based material.
Additionally, another subject matter of the present invention, is to provide a non-destructive process for breakdown and elimination of silicon and/or silicon compounds that are contained in alumina based materials, using an extraction agent that selectively breaks down the silicon compounds that are present in alumina based materials, without modifying substantially other materials or metals that might be present in such alumina based material.
These and other subject matters of the present invention will be established with more clarity and detail in the next chapters.